
/*    This file is part of the managarm operating system.
 *   Copyright (C) 2007, 2008, 2009  Alexander van der Grinten
 *
 *   This program is free software: you can redistribute it and/or modify
 *   it under the terms of the GNU General Public License as published by
 *   the Free Software Foundation, either version 3 of the License, or
 *   (at your option) any later version.
 *
 *   This program is distributed in the hope that it will be useful,
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *   GNU General Public License for more details.
 *
 *   You should have received a copy of the GNU General Public License
 *   along with this program.  If not, see <http://www.gnu.org/licenses/>. */

package org.managarm.jmanaintlib.runtime.system;

import java.io.PrintStream;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.CharBuffer;
import java.nio.charset.Charset;
import java.nio.charset.CharsetDecoder;
import org.managarm.jmanaintlib.machine.VmError;

public class RtPrintStreamChannel extends RtChannel {
	private final PrintStream outputStream;
	private final CharsetDecoder decoder
			= Charset.forName("UTF-8").newDecoder();
	private final ByteBuffer byteBuffer = ByteBuffer.allocate(8);
	
	public RtPrintStreamChannel(PrintStream output) {
		outputStream = output;
		byteBuffer.limit(0); // make sure the buffer is empty
	}

	private synchronized void writeSingle(int databyte) throws VmError {
		try {
			// insert the byte into the byte buffer
			final int limit = byteBuffer.limit();
			byteBuffer.limit(limit + 1);
			byteBuffer.position(limit);
			byteBuffer.put((byte)databyte);
			
			// try to decode the character
			byteBuffer.position(0);
			final CharBuffer buffer = decoder.decode(byteBuffer);
			if(buffer.remaining() > 1) // should never happen
				throw new VmError("Error while decoding utf-8 chars");
			if(buffer.remaining() > 0) {
				outputStream.print(buffer.get());
				byteBuffer.limit(0);
			}
		} catch(IOException e) {
			throw new VmError("Error while reading from stream");
		}
	}
	
	@Override public void writeBytes(byte[] buffer, int offset, int length)
			throws VmError{
		for(int i = offset; i < offset + length; i++)
			writeSingle(buffer[i]);
	}
}
